Laminating apparatus

ABSTRACT

The invention provides an apparatus and a process for producing laminated materials. The process comprises the steps of: (a) supplying material from a first supply roller; (b) supplying materials from a system comprising a plurality of further supply rollers; (c) tracking lateral movement of the material leaving said first supply roller; and (d) adjusting the lateral position of said system in response to said lateral movement, such that the lateral alignment of the plurality of further supply rollers remains constant with respect to the material leaving the first supply roller. The adjustment step (d) may be manual, or it may be automatic e.g. in response to tracking in step (c) by means of an electronic sensor which tracks a control line on the material leaving the first supply roller. By maintaining constant lateral alignment, it is possible to manufacture laminated materials comprising a layer made from strips of material which abut but which do not overlap.

This application is the national phase under 35 U.S.C. §371 of PCTInternational Application No. PCT/GB97/02836 now WO98/16382, which hasan International filing date of Oct. 14, 1997 which designated theUnited States of America.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to apparatus and methods for producing laminatedmaterials, for example such as are used in packaging.

2. Related Art

Goods such as processed food, sweets, medication and liquids are oftenpackaged in material which isolates them from water, gas, vapour, oil,chemicals and the like. This packaging material is usually decorated inorder to distinguish the product from similar goods, for instance, or toprovide directions for use, to list ingredients or to provide statutoryinformation.

Typical material for this purpose is made from single or double layeredtransparent plastics over-printed with the desired design, with doublelayered materials offering better protection to goods.

In order to enhance the visual appeal of a package or to provide adegree of protection against counterfeiting it may also be desirable toadd metallised effects, such as holograms, within such multi-layeredmaterial. The resulting laminated packaging material typically comprisesa sheet of aluminium foil or holographic film sandwiched, and thusprotected, between two sheets of transparent polyethylene orpolypropylene, one or both of which could be over-printed with a design.This material is not transparent, however, due to the presence of theopaque retallised layer.

It would be desirable to have available a packaging material whichincludes a metallised layer but through which the contents of a packageare visible. This could be achieved by sandwiching strips of metallisedmaterial, rather than whole sheets, between outer transparent layers. Inthe regions where the metallised layer is absent the material is thustransparent.

However, simply laminating strips of foil within two plastic layers isnot feasible on a mass production basis. The final laminated materialwill not be of uniform thickness and this will be magnified when it isrolled up, for instance. It is therefore necessary for the middle layerto include strips of transparent material parallel and adjacent to themetallised material to provide a layer with as constant a thickness aspossible.

A desirable laminated material would thus be of substantially uniformthickness, having five layers ie.:

(A) a transparent film made from a material such as polypropylene orpolyethylene, probably decorated with a design;

(B) an adhesive layer;

(C) a layer consisting of a combination of parallel strips of differentmaterials in the same plane or surface. These strips might be, forinstance, lightline aluminium metallised or partially-metallisedlaminating foil, metallised polypropylene film, aluminium foil, ortransparent polypropylene or polyethylene;

(D) a further adhesive layer; and

(E) a heat-sealable or heat-melting film allowing easy application foran automatic packaging system.

Such laminated packaging materials would typically be manufacturedaccording to the following process. The materials which make up layers(A) and (C) are loaded onto separate supply rollers. Material (A)proceeds from its supply roller through a glue tank, where an adhesivelayer (B) is applied to its back surface, and then through a dryingtunnel. The strips which form layer (C) issue from the relevant supplyrollers and meet material (A) emerging from the drying tunnel (A) at anassembly roller. Layer (C) is bonded to adhesive layer (B) to form alaminated material (AC) which is collected on receiving roller.

To complete the packaging material, the laminate (AC) is removed fromthe receiving roller and re-loaded onto a supply roller. The process isrepeated on material (AC), with adhesive being applied to layer (C) andheat-sealable film (E) being attached to form finshed product (ACE)laminate.

A significant problem when manufacturing laminated material in this way,however, is the alignment of the strips in layer (C). The strips, whichmight be of differing widths, will generally issue from separate supplyrollers which might have drums of different diameters and differentmotor speeds. The different materials will tend to have differenttensile strengths, different coefficients of friction, and differentthicknesses.

SUMMARY OF THE INVENTION

During bonding at the assembly roller, aligning the strips in parallelon the same plane or surface without an overlap has so far not beenpossible. Avoiding wrinkles, creases, breakage, and deformation ofstrips during lamination is also difficult. These problems, of course,cause wastage of materials and interruption of the production line.Furthermore, the alignment of the layers at the assembly roller isliable to change due, for instance, to vibration of the machine and forthese reasons current machines and processes of manufacture are, ingeneral, limited to just two strips.

There is thus a need for a laminating process in which the strips whichmake up layer (C) can be accurately aligned relative to layer (A), andin which the strips which make up layer (C) can be aligned withoutoverlap.

According to the present invention there is provided an apparatus forproducing laminated materials having a first supply roller, and a systemcomprising a second and a third supply roller, wherein the lateralpositioning of said system can be adjusted in response to lateralmovement of material which leaves the first supply roller, such that thelateral alignment of the second and third supply rollers remainsconstant with respect to said material.

The lateral positioning of said system may be adjusted manually duringoperation of the apparatus in order to maintain alignment of the secondand third supply rollers with said material. Preferably, however,lateral movement of material which leaves said first supply roller ismonitored by an electronic sensor which tracks a control line in thematerial. The output of the sensor can be used to adjust the position ofsaid system automatically.

The control line can be any feature whose lateral movement can betracked by an electronic sensor. The control line is preferably avisible coloured line but might be, for instance, a thin magnetic strip.Preferably such control lines have a width of 0.5 mm to 3.0 mm. Suchcontrol lines need not be continuous, but they must be electronicallyreadable. Alternatively, the control line can be the edge of thematerial leaving the first supply roller.

The electronic sensor can be any sensor which is capable of accuratelytracking the lateral movement of a control line. Preferably theelectronic sensor can track various types of control line. Suitablesensors are well known in the art for line and edge detection and thesetypically comprise a tungsten lamp and a CdS light detector which picksout very small changes in resistance as the control line meanders.Depending on the reflection efficiency, different filters can be usedwith the detector. For instance, where reflection is efficient a groundglass filter might be used.

Preferably the electronic sensor is fixed to the system comprising thesecond and third supply rollers such that the system and sensor move inconcert.

Preferably the lateral positions of the second and third supply rollersare independently adjustable within the system although during operationof the apparatus the lateral positions should remain fixed relative toeach other.

According to a further aspect of the invention, there is provided aprocess for producing a laminated material comprising the steps of:

(a) supplying material from a first supply roller;

(b) supplying materials from a system comprising a plurality of furthersupply rollers;

(c) tracking lateral movement the material leaving said first supplyroller; and

(d) adjusting the lateral position of said system in response to saidlateral movement, such that the lateral alignment of the plurality offurther supply rollers remains constant with respect to the materialleaving the first supply roller.

Whilst adjustment step (d) may be effected manually, it is preferablyeffected automatically. For instance, the output of an electronic sensorwhich tracks lateral movement in material leaving the first supplyroller may be used to control the lateral positioning of the pluralityof supply rollers automatically.

Preferably, therefore, tracking step (c) involves tracking lateralmovement in a control line in the material leaving said first supplyroller by means of an electronic sensor.

The materials leaving said plurality of further supply rollers shouldall be of substantially the same thickness as each other. Preferably oneor more of these materials is a holographic or metallic material.

The positions of the plurality of further supply rollers should be fixedrelative to each other, such that their lateral positions remainconstant with respect to each other. Preferably the plurality comprises3 or morb supply rollers.

According to a further aspect of the invention, there is provided alaminated material obtainable by a process as set out above.

Similarly, the invention also provides a laminated material comprising alayer made up of a plurality of parallel strips of material which abutand do not overlap.

Preferably the layer made up of abutting strips comprises at least threestrips, one or more of which is a holographic or metallic strip.Preferably such a strip is bordered by transparent or translucentstrips. More preferably, the layer comprises strips of transparent ortranslucent material alternating with opaque strips (eg. made fromholographic or metallic material).

The layers will typically be joined to each other by adhesive.Accordingly, the invention provides laminated material having atransparent layer, an adhesive layer, and a layer comprising a pluralityof parallel strips of material which abut and do not overlap. One ofsaid strips is preferably a holographic or metallic strip Of course, itwill be appreciated that said “transparent” layer may be over-printedwith a design, for instance, which renders it only partiallytransparent.

These laminated materials may also comprise further layers. Preferably,therefore, the invention provides a laminated material as above, furthercomprising a fourth layer. This fourth layer may, for instance, be aheat-sealable layer or a layer of adhesive. The laminated material mayalso comprise a fifth layer, which may be made from the same material asthe first layer, for instance, or may be a heat-sealable layer.

These laminated materials can be used for shrink-wrapping, for example,or during the manufacture of bags or pouches.

The invention also provides the use of a electronically-readable controlline on material leaving a first supply roller to control the alignmentof a plurality of further supply rollers with respect to said material.

BRIEF DESCRIPTION OF THE DRAWINGS

A specific preferred embodiment of the invention will now be describedby way of example with reference to the accompanying drawings in whichFIG. 1 illustrates the apparatus and FIG. 2 shows the materials beinglaminated at the assembly roller (8).

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The apparatus in FIG. 1 is for bonding two layers (A) and (C) to form alaminated material. Layer (A) might, for example, be a transparent filmmade from polyethylene, over-printed with a design. Layer (C) is formedfrom a series of adjacent parallel strips (C₁, C₂, C₃, . . . ) whichabut and do not overlap. The strips might, for instance, be a widetransparent strip (C₁) abutting with a thin metallised holographic strip(C₂) abutting with a wide translucent strip (C₃)

Transparent film (A) is loaded onto supply roller (1) and its tension isadjusted. Similarly, the strips (C₁, C₂, C₃, . . . ) which form layer(C) are loaded onto supply rollers (7) which are mounted in system (5).The tensions of the supply rollers (7) are adjusted and the rollers (7)are laterally arranged such that the edges of the strips leaving therollers (7) which make up layer (C) will abut.

During operation film (A) proceeds through the glue tank (2), whereadhesive layer (B) is applied to its back surface, and then into dryingtunnel (3).

Film (A) with adhesive layer (B) emerges from the drying tunnel (3) andreaches a point where electronic sensor (4) is situated. In thispreferred embodiment, film (A) contains a control line (X) which isstill electronically readable through the dried adhesive layer (B).Electronic sensor (4) is initially positioned so that control line (X)will be within its range of detection when film (A) passes beneath.

In the course of the laminating process, small lateral changes in thetravel path of film (A) occur. The electronic sensor (4) detects thesechanges by tracking the position of the control line (X) in film (A) andtransmits details of these changes to system (5) which comprises asupporting frame (6) on which a plurality of supply rollers (7) aremounted and secured. Each roller (7) is independently laterallyadjustable vis-a-vis the other rollers (7) but during operation therollers (7) are fixed relative to each other. Each roller (7) possessesits own speed reducer motor and tension detector.

In response to the signals from sensor (4), the lateral position ofsystem (5) is adjusted. Rollers (7) thus move together relative toassembly roller (8) and the alignment of material (A) and the materialsfrom rollers (7), which make up layer (C), remains constant.

As shown in FIG. 2, tie strips (C₁, C₂, C₃, . . . ) forming layer (C)emerge from system (5) precisely aligned with film (A). At heatedassembly roller (8) layer (A) meets the strips which form layer (C). Thestrips are bonded to adhesive layer (B) to form a laminated material(AC) which is collected on receiving roller (9)

To complete the packaging material, the laminate (AC) is removed fromreceiving roller (9) and re-loaded onto supply roller (1), After dueadjustment of tension, the process is repeated on material (AC ), withadhesive being applied to layer (C) and heat-sealable film (E) beingattached to form finished product (ACE) laminate.

The laminate (ACE) is left at an appropriate temperature for about 12 to48 hours to let the layers settle before being used for packaging.

It will be understood that the invention is described above by way ofexample only and modifications may be made within the scope and spiritof the invention.

What is claimed is:
 1. A process for producing a laminated materialcomprising the steps of: (a) supplying material from a first supplyroller; (b) supplying materials from a system comprising a plurality offurther supply rollers, the materials being laterally aligned in anabutting, non-overlapping relationship; (c) tracking lateral movement ofthe material leaving said first supply roller; (d) adjusting the lateralposition of said system in response to said lateral movement, such thatthe lateral alignment of the plurality of further supply rollers remainsconstant with respect to the material leaving the first supply roller.2. A process according to claim 1, wherein step (c) comprises trackinglateral movement in a control line in the material leaving said firstsupply roller by means of an electronic sensor.
 3. A process accordingto claim 1, wherein the plurality of further supply rollers comprises 3or more supply rollers.
 4. A process according to claim 1, wherein thematerials leaving said plurality of further supply rollers are all ofsubstantially the same thickness as each other.
 5. A bag made fromlaminated material according to claim
 1. 6. An apparatus for producinglaminated materials, having a first supply roller and a systemcomprising a second and a third supply roller, wherein the lateralpositioning of said system can be adjusted in response to lateralmovement of material which leaves the first supply roller, such that thelateral alignment of the second and third supply rollers remainsconstant with respect to said material.
 7. An apparatus according toclaim 6, further comprising an electronic sensor which tracks a controlline in thy material leaving said first supply roller.
 8. An apparatusaccording to claim 7, wherein said control line is a visible colouredline.
 9. An apparatus according to claim 7, wherein said control line isthe edge of the material leaving said first supply roller.
 10. Anapparatus according to claim 7, wherein said electronic sensor is fixedto said system much that the system and sensor move together.
 11. Anapparatus according to claim 7, wherein the lateral positions of thesecond and third supply rollers are independently adjustable within saidsystem.